The present disclosure generally relates to methods and compositions for decreasing water permeability within a subterranean formation, and, more specifically, to relative permeability modifiers formed from acrylamide polymers and use thereof in a subterranean formation, particularly a carbonate formation.
Treatment fluids can be used in a variety of subterranean operations. Such subterranean operations can include, without limitation, drilling operations, stimulation operations, production operations, remediation operations, sand control treatments and the like. As used herein, the terms “treat,” “treatment” and “treating” refer to any subterranean operation that uses a fluid in conjunction with achieving a desired function and/or for a desired purpose. Use of these terms does not imply any particular action by the treatment fluid or any component thereof, unless otherwise specified herein. Illustrative treatment operations can include, for example, fracturing operations, gravel packing operations, acidizing operations, scale dissolution and removal operations, consolidation operations, and the like.
When performing these or other subterranean treatment operations, it can sometimes be desirable to suppress the flow of a fluid in a subterranean formation. It can be particularly desirable to suppress the flow of an aqueous fluid in the subterranean formation, especially during production of a hydrocarbon resource from the subterranean formation. When a subterranean formation contains water in significant quantities, water's high mobility often allows it to flow to a wellbore by way of natural and manmade fractures and high permeability subterranean zones. The unwanted production of water from a hydrocarbon-producing well can constitute a considerable technical problem and expense during oilfield operations. If the ratio of produced water to a produced hydrocarbon resource becomes sufficiently large, the cost of separating the water from the hydrocarbon resource and disposing of the water can become a barrier to continued production. Excessive water production can even lead to abandonment of a wellbore penetrating a subterranean formation, even when significant amounts of hydrocarbons remain therein.
In some instances, various polymer systems can be introduced to a subterranean formation in order to form a temporary or permanent fluid seal therein. Through judicious placement of the fluid seal, a decrease in water production can sometimes be realized while not overly impacting the production of a hydrocarbon resource. Selective placement of the polymers under the formation conditions can sometimes be problematic, and improper placement of a fluid seal can sometimes detrimentally impact hydrocarbon production. In such situations, an agent that is not dependent upon judicious placement methods and does not cause detrimental results when improperly placed in a subterranean formation can be particularly desirable.
In regard to the foregoing, a technique that has been used to decrease the production of water, primarily from siliceous formations, is to introduce a relative permeability modifier to the formation. As used herein, the term “relative permeability modifier (RPM)” refers to a substance that decreases the flow of water in a subterranean formation while having a minimal effect on the flow of hydrocarbons. Since they minimally impact the flow of hydrocarbons, relative permeability modifiers can often be introduced to a subterranean formation without employing zonal isolation techniques that can be commonly employed with other agents (a strategy known as “bull heading” of the treatment fluid). Illustrative relative permeability modifiers can include both hydrophobically modified hydrophilic polymers and hydrophilically modified hydrophilic polymers, such as those described in commonly owned U.S. Pat. Nos. 6,476,169 and 7,114,568. An illustrative commercial relative permeability modifier product is HPT-1, which is a cationic hydrophobically modified hydrophilic polymer available from Halliburton Energy Services in its WATERWEB treatment service.
Permeability modification of aqueous fluid flow in subterranean formations can sometimes beneficially suppress treatment fluid loss to high permeability subterranean zones. Such fluid loss may occur in various subterranean operations including, for example, flooding operations in enhanced oil recovery, establishing fluid recirculation in drilling, cementing, fracturing and gravel packing operations, and diverting operations, such as those employed in acid stimulations.
When hydrophobically modified hydrophilic polymers are used in treating a siliceous formation, such as a silicate, aluminosilicate or like siliceous formation, prolonged reduction of the water permeability within the formation can often be realized. In contrast, when employed under similar conditions in a carbonate formation, the water permeability reduction effect is frequently much less sustained over an extended period of time. Although a cationic RPM can be reapplied to a carbonate formation once the initial water permeability reduction has waned, such retreatment can be undesirable from a time and materials standpoint, both of which increase production costs. While sustained water permeability reduction is not always necessary, such as during short-term diversion or fluid loss control operations, it can be desirable in many cases, particularly during ongoing production operations in producing wells.